A wide variety of fluid absorbent structures known in the art are useful for absorbing body fluids such as blood, urine, and menses. Ideally, these products should be sanitary and comfortable in use. Disposable absorbent products of this type generally comprise a fluid-permeable topsheet material, a fluid absorbent core, and a backsheet material. Various shapes, sizes and thicknesses of such articles have been explored in an attempt to make their use more comfortable and convenient.
Odor control and odor masking in disposable absorbent products has been researched from a number of different perspectives over the years to alleviate the discomfort that accompanies unpleasant odors during use of such products, Additionally, such products, after use, often develop an especially unpleasant odor and require special handling and disposal to mitigate and contain the unpleasant odor. For instance, many bodily fluids have an unpleasant odor, or develop such odors when in contact with air and/or bacteria for prolonged periods. Consumers typically use malodor to determine the need for change of a diaper, catamenial and the like. For example, malodor is also an integral component of the toilet training process for both caregiver and infant wearer.
One alternative to relying on body malodor as one factor to indicate the need to change the disposable absorbent product is through the use of a “scent signal.” A “scent signal” is a positive perfume odor which signals to a consumer the need to at least inspect, if not remove the absorbent product. Alternatively, the scent signal may merely work to neutralize or mask the malodor caused when bodily exudates contact the atmosphere in such a way that others are not offended by the smell of the wetted product. Typically, the scent signal is released when contacted by bodily fluids, such as sweat, urine, menses and the like.
One material which is suitable for incorporation into absorbent products to generate a scent signal are the starch encapsulated perfume accords, or SEA. SEAs are generally solid particles comprising water-soluble cellular matrixes containing perfume stably held in the cells. Encapsulating specific ingredients in a starch-based encapsulate is well known where it is desired to form a water-soluble barrier between the component ingredients and its environment. The encapsulation is usually to protect a sensitive ingredient from its environment, or vice versa. When SEAs are contacted with water, such as moisture, urine, menses, etc, or exposed to high water vapor content gas (relative humidity), the water-soluble cellular matrix at least partially dissolves or is plasticized thereby allowing for the perfumes release, thereby generating a scent signal.
In addition, for perfumes there is an additional factor that consumers do not like to be overwhelmed by strong perfume odors on opening a bag or other container of diapers or absorbent product. In order to provide sufficient odor fragrance scent, when wet, a relatively high amount of perfume is needed. However, high levels of perfume tend to make unacceptably strong odor for the dry, unused, diaper or absorbent product itself. Encapsulation was therefore developed as a way of introducing more perfume into a product where it is desired that the product itself should not have a very strong odor when dry, and generate a scent signal, when wet.
The manufacture of starch particle encapsulates is related to the production of fine particulate material during manufacture. Since these materials are flammable, a build up of very fine particles may be explosive in the presence of oxygen and a source of ignition such as a spark. Though it would be advantageous to incorporate SEA particle encapsulates into absorbent products to provide a scent signal, there are numerous problems associated with their manufacture. An area of improvement for adding SEAs particles to an absorbent product, generally relates to the need for accuracy in the incorporation of SEA particles onto a substrate. For instance, it is difficult and costly to be able to deliver SEA particles to a substrate with any degree of reasonable accuracy required for a commercial process. Typically, these problems are related to preventing or minimizing the SEAs exposure to moisture and reducing and/or eliminating the potential for the SEAs particles to generate dust during manufacture and during incorporation into the absorbent product. For instance, they require a carrier media that permits storage and facilitates transport to the intended surface in the absorbent product. Typically, this carrier requires heating and mixing prior to application of the SEA to the substrate's surface. A proposed solution to these processing problems is detailed in US Patent Publication 2004/0241333 A1 (Cielenski et al.) published on Dec. 2, 2004.
Applicants have determined that it would be just as advantageous to provide a perfume, in an oil-in-water emulsion composition comprising a water soluble encapsulant, which is a modified starch, that is able to retain its stability over extended period of times without the need for additional mixing, blending, or heating immediately prior to application of the composition to a substrate surface. Ideally, this mode of manufacture will afford flexibility to yield either 1) a negligible level of ‘surface free perfume oil’ upon dehydration or 2) some ‘free perfume oil’ upon dehydration of the oil-in-water emulsion. A negligible level of amount of “surface free oil” will minimize perfume lost to evaporation, such that the overall manufacturing process becomes more efficient and the end user realizes the full benefit of the perfume as delivered to the disposable absorbent article when released and made wet. Having some amount of ‘surface free oil’, upon dehydration of the emulsion, affords the opportunity to connote fragrance odor to the dry product, separate and in addition to fragrance expressed, upon wetting of the dehydrated oil-in-water emulsion, if necessary to mask and offset other odors associated with the absorbent article's manufacture, e.g, adhesives.